60 



TEMPERATURE. 



Table 24. 

 ' McMurdo ' Type. 



The two example.s under the Fram type show the maximum amplitude early in the spring 

 after which the ampUtude decreases until midsummer. In the case of the Fram there is a 

 temporary rise during August before the amplitude begins to decrease to its \vinter value. 



The amplitade in the second type increases until the summer is reached, and it is 

 interesting to notice that in each case tho warmest of the three summer months shows a 

 slight decrease ir the amplitude as compared with the months on either side. 



Both Professor Mohn and Professor Meinardus have given explanations of the Fram type, 

 both are different and both appear not to be the full explanations. A discussion of these 

 two explanations will be fruitful iu shov^lng some important factors connected with the tempera- 

 ture of polar regions and therefore I propose to give their explanations, point out where they 

 fail, and then attempt to give a true explanation. 



Professor Malm's Explanation of the ' Fratu ' Type of Daihj Teitiperuture Variation.— M.ohi\ fii-st 

 examines the effect of cloud and wind on the daily variation of temperature and finds that both 

 these factors reduce the amplitude. The effect of the cloud is to reduce the variations in 

 solar radiation and radiation from the surface, while the wind stirs up the lower atmosphere 

 and distributes the effect of the varying temperature of the gromid through a laige mass of 

 the atmosphere. He also calculates the 'difference in the amount of solar energy received 

 on each square centimetre of surface at midday and midnight, on which the temperature 

 variation must ultimately depend. 



We will now quote from page 605 of Mohn's discussion : — 

 ' In the following table I hava put together the mean monthly values of (1) the diurnal 

 amplitude f of the radiation of the sun and sky, a ; (2) the amount of cloud, c ; 



The data for Framheim are only approximate. At tliis station temperature observations -were taken only 

 at o A.M., 2 P.M. and 8 p.m. As.suming as a rough approximation that the mean of the 8 a.m. and 8 p.m. 

 observations gives the mean of the day and tliat the 2 p.m. observation is near the maximum, the approximate 

 amplitude has been taken as twice the excess of the 2 p.m. mean above the mean of the 8 a.m. and 2 p.m. 

 observations. 



tl have taken the liberty of altering Hie -n-ord 'range' u.scd by Muhn into 'amplitude' in oitler to keep 

 tile use of tlieae two words consistent tliroughout this work. 



